The use of graphite/epoxy materials for building aircraft structures is expanding. For example, graphite/epoxy "I" stiffeners are +being used to give strength and rigidity to the empennage of new aircraft. In order to keep pace with this expanding use of these new materials, new and faster methods for inspection are required.
In general, ultrasonic systems, whether multiple or single channel (a pair of transducers, transmitting and receiving) requires repeated passes over the part for 100% ultrasonic inspection of the part. This is a time consuming procedure.
The present invention, hereinafter described "feedthrough stiffener inspection system" (FSIS), provides a rapid ultrasonic inspection of the aforementioned "I"-shaped stiffeners. FSIS is a one pass, 100% inspection capable of handling stiffeners, regardless of length. FSIS's transducers are stationary, which eliminates the need for long cables (a problem characteristic of devices which creep along the stiffener while inspecting or gantry-type robots). Also, because FSIS is stationary, one person can control movement of the part through the system and evaluate the inspection data at the same time. Because FSIS is an immersion ultrasonic technique, its transducer shoes are much more simple and cost effective to design and manufacture than those of other inspections which are relegated to using a bubbler technique. Compared to other immersion techniques, FSIS is a faster technique. Due to its small size, FSIS does not require a large storage area while not in use.
In accordance with the present invention, there is provided a feedthrough stiffener inspection system for determining the presence, location, and size of flaws in the radius region and adjacent areas of a structure. A preferred embodiment of the present system comprises: 6 probes with a plurality of transducers; an immersion tank with "I"-shaped windows fore and aft; a water collection tank; a fore and aft motor drive assembly; a fore and aft position encoder assembly; a water recirculation system; and, a plurality of roller tables.
In accordance with further features of the present invention, the probe assembly further comprises a plurality of individual shoes configured for complementary engagement with the structure under inspection. The individual shoes are pushed toward each other by spring assemblies so as to clamp the "I" stiffener. The plurality of transducers inspect the "I" stiffener and produce relevant inspection information.
In accordance with further features of the present invention, the fore and aft motor assemblies are mounted to a spring-loaded platform which pushes the motor assemblies against the "I" stiffener. A pressure wheel with movable platform is directly opposite the motor drive wheel. The interaction of the two wheels create the translational movement of the "I" stiffener enabling it movement through the immersion system. The fore and aft motor assemblies operate synchronously.
In accordance with yet further features of the present invention, the position encoder assemblies are mounted to a spring-loaded platform. The relative motion of the structure moving through the system drives the encoder, thereby producing position information for generating C-scans. The fore and aft position encoder assemblies operate synchronously. As the structure moves through the system, the fore encoder electronics is activated. When the structure disengages from the fore position encoder, the aft encoder is activated until the structure disengages from the aft encoder.
In accordance with still further features of the present invention, the recirculation system maintains the water level of the immersion tank so that the "I" stiffener and probes are always immersed. The recirculation system recycles the water from the collection tank back into the immersion tank.
In accordance with yet further features of the present invention, conveyor tables fore and aft of the immersion system support the structure as it moves through the inspection station.